Conventionally, a display panel of a so-called active matrix driving system constituted by a thin film transistor (hereinafter also referred to as a “TFT”) over a glass substrate is known. This active matrix display panel is manufactured by patterning various thin films by a light-exposure step using a photomask, similarly to a manufacturing technique of a semiconductor integrated circuit.
Until now, there is employed a manufacturing method for cutting out plural display panels from one mother glass substrate and mass-producing efficiently. The size of a mother glass substrate used for manufacturing display panels is increased from 300 mm×400 mm of the first generation in the early 1990s to 680 mm×880 mm or 730 mm×920 mm of the fourth generation in 2000. Furthermore, the manufacturing method has been developed so that a large number of display panels can be obtained from one substrate.
When a size of a glass substrate or a display panel is small, a patterning treatment can be carried out comparatively easily by using a photolithography apparatus. However, as a substrate size is increased, an entire surface of a display panel cannot be simultaneously treated by carrying out a light-exposure treatment once. Consequently, a method for exposing an entire surface of a substrate to light has been developed as a light-exposure treatment. (for example, consecutive light-exposure to one substrate for connecting edges of elements such as a wiring not to be disconnected at a boundary between the elements). This method is performed by dividing a region where a photoresist is applied into a plurality of block regions, carrying out a light-exposure treatment on every predetermined block regions, and by sequentially repeating them (for example, Reference 1: Japanese Patent Laid-Open No. Hei 11-326951).